WYSIWYG comments gray text in black background

I’m using bbPress (last version, with lastest WP too in a single site) and have the General Forums activated (not the group ones). I activated the option to use the WP WYSIWYG visual editor for the comments, which had a black background and a white text color. Usually it worked very well, but one day (too far ago), the color of the text changed to gray (check the image below).

I don’t remember changed anything on the code. Maybe it was a plugin update or something like that, but I couldn’t change it back.